Photothermographic substance



United States Patent PHOTOTHERMOGRAPHIC SUBSTANCE Marilyn Levy, Red Bank, N. .L, and Heinz Schulze, Binghamton, N. Y., assignors to the United States of America as represented by the Secretary of the Army No Drawing. Application June 6, 1956, Serial No. 589,830

3 Claims. (Cl. 964) (Granted under Title 35, U. S. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment of any royalty thereon.

This application is a continuation-in-part of our copending application Serial No. 440,308, filed June 29, 1954, now Patent No. 2,759,819.

This invention relates to new photothermographic substances, and to photographic layers sensitized with the new photothermographic substances.

The term photothermographic has been defined in U. S. Patent 2,095,839 as characterizing a material which after its exposure to light may be decomposed or modified by the action of heat diiferentially in accordance with the exposure to light. A photographic layer sensitized with such photothermographic substances is therefore, after exposure to light, developable by heat.

The present invention is based on the discovery that the silver salts of malondiamidoxime and glutardiamidoxime are valuable thermographic substances which will produce after exposure to light and subsequent to heat treatment a visible record of the incident light.

The invention will become more apparent from the following description of concrete embodiments of the inventive idea.

EXAMPLE 1 1. Preparation of malondiamidoxime Malondiamidoxime was prepared according to the method of Schmidtmann. (See: Berichte der Deutchen Chemischen Gesselschaft, vol. 29, p. 1169.)

2. Preparation 0 silver salt of malondiamidoxime Dissolve 1.32 gms. of malondiamidoxime in 50 ml. H2O on steam bath. Cool to about 35 C. and add 20 ml. of a 1 normal solution of silver nitrate in water. After adding 2 cc. of a 1 normal solution of ammonium hydroxide, a white curdy precipitate is formed. Filter and wash with distilled water and dry over night in a vacuum desiccator over calcium chloride. The precipitate is then ground in an agate mortar.

The gelatin emulsion of the silver salt of malondiamidoxime is prepared by adding five ml. of a 3 percent gelatin solution at 40 C. to 1.5 grams of dried silver malondiamidoxirne ina dried container with agitation. When the silver salt is thoroughly wetted, 25 ml. of a gelatin solution (3 percent at 40 C.) is added to the above mixture. The emulsion formed, is then passed through a warmed, stainless steel, hand homogenizer and coated on clean glass slides. These slides were exposed to a light source and thermal development was carried out by placing the plate, emulsion-side up, in a Nichromewound aluminum block oven at 102 C. for about four minutes.

The light sensitivity of silver malondiamidoxime depends 011 t e following factors; I

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(a) Variation of ratio of silver nitrate (AgNOa) to malondiamidoxime in the preparation of the silver salt.

Silver salts were prepared containing 1 mole, 1 /2 mole, 2 mole and 2 /2 mole of AgNO3 to 1 mole of malondiamidoxime and it was found that the light sensivity increases with increased AgNOs, although the change is not substantial.

(b) Type of gelatin usedto disperse the silver salt.

Inert, moderately inert, moderately active and active grades of gelatin were used as a dispersing medium for the silver salt of malondiamidoxime. It was found that the greatest sensitivity was exhibited by films using the inert gelatin as a carrier and poorest sensitivity using the active gelatin. The remaining gelatins gave intermediate values between these two extremes.

(c) Variation in the ratio of silver salt to gelatin in the emulsions.

The light sensitivity increases with increased ratio of silver salt to gelatin. Optimum conditions of light and heat development were obtained using the ratios prescribed in the directions given previously for the preparation of gelatin emulsions of silver malondiamidoxime.

EXAMPLE 2 1. Preparation of glutardiamidoxime Glutardiamidoxime is prepared according to the method of Biedermann. (See: Berichte der Deutschen Chemischen Gesellschaft, vol. 22, p. 2967.)

2. Preparation of silver glutardiamidoxime Dissolve 1.60 gms. glutardiamidoxirne in 25 ml. absolute alcohol. mal solution of silver nitrate in 50/50 solution of absolute alcohol and water. Filter and wash with absolute alcoholwater solution.

The gelatin emulsion of the silver salt of glutardiamidoxime is prepared as described in Example 1.

The photothermographic substances according to the invention may be dispersed in any suitable colloidal carrier to produce a photothermographic layer on one of the conventional supports. The material for the photographic layer may consist of gelatin, casein, agar, and various natural or synthetic high polymers such as polystyrene or phenol formaldehyde resins, vinyl resins, alkyd resins, etc. The support for the photographic layer may be a plate of any of the commonly used materials such as glass, paper, cellulose derivatives, etc.

It will be obvious to those skilled in the art that a great many variations and combinations of the described processes are possible within the broad inventive idea as characterized in the appended claims.

What is claimed is:

1. A photothermographic element comprising a support and a photothermographic layer, said layer compris ing an organic colloid carrier having dispersed therein a member selected from the group consisting of silver malondiamidoxime and silver glutardiamidoxime.

2. A photothermographic element comprising a support and a photothermographic layer, said layer comprising an organic colloid carrier having dispersed therein silver malondiamidoxime.

3. A photothermographic element comprising a sup port and a photothermographic layer, said layer comprising an organic colloid carrier having dispersed therein silver glutardiamidoxime.

No references cited.

Cool to about 35 and add 20 cc. 1 nor- 

1. A PHOTTHERMOGRAPHIC ELEMENT COMPRISING A SUPPORT AND A PHOTOTHERMOGRAPHIC LAYER, SAID LAYER COMPRISING AN ORGANIC COLLOID CARRIER HAVING DISPERSEDS THEREIN A MEMBER SELECTED FROM THE GROUP CONSISTING OF SILVER MALONDIAMIDOXIME AND SILVER GLUTARDIAMIDOXIME. 